The present invention relates to a mobile radio telecommunications system having a battery saving capability and, more particularly, to a mobile radio telecommunications system capable of saving power to be consumed by mobile stations.
Various forms of battery saving system for a mobile radio telecommunications system have been proposed. An intermittent reception system is one form of a conventional battery saving schemes, where it groups a plurality of mobile stations according to certain rules. In this kind of system, a particular time for starting broadcasting terminating call signals is assigned to each group of the mobile stations. A base station starts broadcasting terminating call signals meant for the associated group of mobile stations at the assigned time. The mobile stations receive terminating call signals only during an interval for which, among the terminating call signals being broadcast from the base station, only the signals meant for the subscriber group to which they belong are broadcast. This kind of scheme is disclosed in, for example, "DIGITAL CELLULAR TELECOMMUNICATION SYSTEM", RCR STANDARD, RCR STD-27B, pp. 473-480.
Japanese Patent Laid-Open Publication No. 63-199526, for example, teaches a battery saving system which causes a base station to send system information or terminating call information including timing information. The timing information indicates the time for a mobile station to receive the necessary system information or terminating call information. This kind of system makes it needless for the mobile station to maintain a device thereof for receiving the system information or call terminating information in a reception state at all times. Hence, the power saving feature is achievable even if the interval between the reception of one system information and that of the next system information is not constant.
The systems described above have some issues yet to be solved, as follows. The systems each reduces power to be consumed by a mobile station when the mobile station receives system information or terminating call information being broadcast from a base station. But, a mobile station, which has sent a signal to a base station, does not know beforehand the time when the base station will return a response signal thereto. This forces the mobile station to feed power to a receiver thereof, i.e., prepare it for reception at the earliest time when it may receive a response signal from the base station. As a result, the power consumption of the mobile station is increased in proportion to the delay in the return of the response signal from the base station.